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Understanding Ductless Mini Splits & How They Work

October 20, 2014

Technology has seen some amazing achievements in the past few decades. Ductless mini splits are one of the greatest triumphs in commercial and residential heating technology, combining quality performance with improved costs.

This advanced technology has been around for over 60 years, finding great global popularity, but ductless mini splits have only recently made a splash in North America. With the addition of inverter technology, mini splits are more popular than ever. Let’s take a minute to learn what these systems are, how they work, and why they’re so efficient.

Ductless Air Conditioning

What Are Ductless Systems?

Ductless mini split systems offer heating and cooling in one quiet, compact, and energy-efficient package. Like standard systems, mini splits are comprised of two primary components: an indoor unit and outdoor unit(s). The outdoor unit houses the condenser and compressor. The indoor unit conditions the air and returns it right back to the room without the need for a ducting system.

The two components are connected via a conduit containing:

  • Electrical wires/power cables
  • Condensate drain lines
  • Refrigerant tubing

This conduit line is fed through a small hole in the wall to the outdoor unit and is concealed in a plastic cover. You can connect several indoor air handling units to a single outdoor unit, assigning each air handling unit to a different room. You can then control each air handling unit with its own thermostat.

Ductless air conditioning San Diego

How It Works

When you grab your remote and turn on your ductless system, the indoor unit tells the outdoor condenser that you want it cool. The outdoor unit tells the compressor and outdoor fan to start working at just the right level to achieve the temp you want.

The compressor in the outdoor unit compresses refrigerant to a high pressure and pumps it thru sealed refrigerant lines to your indoor cassette. A small device called an expansion valve acts like a restriction and only allows a small amount of refrigerant thru the other side. This creates a large pressure and temperature drop, which converts the liquid refrigerant into a gas.

Now the refrigerant is primed and ready to soak up a lot of heat from the air that passes over the coil in the indoor unit. The refrigerant, in a gas state, carries it’s payload of heat back to the outdoor unit where it is compressed again and releases it’s heat thru the fan pulling air across the outdoor coils. Next time your air conditioning is running go outside and feel the air coming off the condenser, it will be nice and hot! Finally as the compressed refrigerant gives off heat, it reverts back to a liquid state again and travels back inside to continue the cycle all over again!

No Ducts, No Problem

Part of what makes ductless cooling and heating systems efficient is the lack of ducts. With improper maintenance or old equipment, ducts can account for significant energy loss. Up to 30% of the air that moves through your ducts is lost thanks to holes, leaks, and poor connections. This becomes especially true in unconditioned spaces, like your attic.

With a ductless system, you don’t have to worry about these energy losses, nor do you have to think about the general upkeep and associated costs that go into maintaining your ducts.

The Compressor

The compressor is the heart of any cooling system, acting as a pump that puts the refrigerant gas under high pressure—part of the process of turning the refrigerant back into a liquid. A standard fixed-speed scroll compressor starts when the thermostat is turned on, runs at full speed, and turns off once the room reaches the desired temperature. This uses a lot of energy and isn’t very efficient. There are also 2-stage compressors, which are a little more efficient.

A ductless inverter compressor is unique in that it can vary its power and performance to match exactly what’s needed in the home. Inverter compressors generally stay on standby idle, making incremental changes to maintain a consistent temperature. This offers much more efficient cooling and heating. It also allows the system to control multiple indoor units in different rooms of the house! Research shows that inverter compressors reduce power consumption up to 60% over a standard fixed-speed compressor.

Ductless mini split systems are an amazing, money-saving investment. In part two, we’ll take a look at the environmental and financial benefits of having a ductless system in your home.

About The Author

Bob Jenson

For over 45 years, Bob Jenson has been providing quality heating and air services to the San Diego community.

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